Collagen-induced arthritis (CIA) is an experimental model of autoimmune arthritis that shares important immunopathological and clinical features with human rheumatoid arthritis (RA). We have previously identified the major T cell determinants recognized by T cells from I-A r (B 10.RIII) mice. Recombinant CB 10 has been engineered to contain a mutated T cell determinant with the resulting mrCB 10 successfully inducing arthritis. Recently, we have observed that adding an additional arthritogenic T cell epitope to the carboxyl terminus of mrCB10 significantly increases the incidence and severity of arthritis, while second determinants placed in other positions had no effect. This data indicates that the T cell epitope plays a critical role in determining whether a particular CB fragment is arthfitogenic and that there are positional and structural constraints that affect the arthritogenicity of the second T cell determinant. Aim 1 will determine whether the position of the T cell determinant within the recombinant protein influences its ability to enhance arthritis. A panel of genetically engineered mutants of rCB 10 will be generated and tested for arthritogenicity by immunizing groups of 10 B 10.RM mice and evaluating the incidence and severity of arthritis. The dependency on antigen processing of the T cell determinant placed in various positions within rCB10 will be investigated in Aim 2. The mutant recombinant peptides will be tested for the ability to bind to MHC. Antigen presentation and T cell stimulation assays will also be used to determine the relationship between antigen processing and the location of the antigenic determinant. Finally, the characteristics of the CII-specific T cells that are critical for eliciting CIA will be assessed in Aim 3. Selected mutant CB10 peptides will be used to immunize mice and a panel of T hybridomas will be generated and tested in vitro against linear peptide, full length mutant peptide, and a panel of analog peptides to determine whether the T cells generated are type A or type B. "Type A" T cells that recognize the MHC-bound classically processed peptide will be compared with "type B" T cells that recognize only exogenous peptide. T cells will be tested for proliferation, cytokine profiles, and phenotype. A better understanding of the determinants which are recognized by T cells as well as a better characterization of the types of T cells which are arthritogenic should allow us to target particular T cells for the development of immunotherapeutic reagents capable of down-regulating arthritis. Moreover it is possible that tolerogens or altered peptide ligands that take into account both types of A and B T cell determinants may possess enhanced therapeutic potential. [unreadable] [unreadable] [unreadable]